Field of the Invention
The present invention relates to phosphate ceramic hard tiles. Hard tiles cover surfaces, and must be curl resistant, dimensionally stable and have high strength and density. Hard floor tiles in particular need high strength and density.
Ceramics made with phosphoric acid, calcium silicate, and metal oxides are described in U.S. Pat. No. 4,375,516. This reference relates to both foamed and non-foamed phosphate ceramic compositions which are recognized as useful for the preparation of building and insulating materials. The properties needed for hard tiles, and in particular, for hard floor tiles, however, are not found. Flexural strength and density of the phosphate ceramics, in particular have been found to be too low for hard tiles. This particular kind of tile (hard tiles) are required to be highly durable, especially the flooring tiles.
Previously, ceramics would have adequate breaking strength only at impractically large dimensions of thickness, and even then still lacked adequate flexural strength, durability, and density to provide hard tiles.
The present application, however, provides phosphate ceramic hard tiles which have the superior strength, high density, and the flexural and breaking strength needed in hard tiles. Characteristically the tiles also have a high degree of dimensional stability.